Permanent-magnetically excited electrical motor

ABSTRACT

A permanent-magnetically excited electric machine comprising a stator part ( 2 ) and a moving part ( 30 ) movable relative to the stator part ( 2 ), as well as an air gap ( 8 ) between the stator part ( 2 ) and the moving part ( 30 ), with one of said stator part ( 2 ) and said moving part ( 30 ) having a flux path assembly for magnetic flux and winding coils ( 6 ) and the other one of said stator part ( 2 ) and said moving part ( 30 ) having a flux path assembly for magnetic flux and permanent magnets ( 36 ), characterized in that there is provided a flux conduction liquid ( 18 ) that is conductive for magnetic flux; and that in the region of the flux path assembly of the stator part ( 2 ) and/or of the moving part ( 30 ), there is provided at least one filling space ( 12; 16; 20; 38; 46; 48; 50 ) which, for changing the magnetic flux conductivity of the flux path assembly, may have optionally more or less flux conduction liquid supplied ( 18 ) thereto.

The invention relates to a permanent-magnetically excited electricmachine comprising a stator part and a moving part movable relative tothe stator part, as well as an air gap between the stator part and themoving part, with one of said stator and moving parts having a flux pathassembly for magnetic flux and winding coils and the other one of saidstator and moving parts having a flux path assembly for magnetic fluxand permanent magnets.

The electric machine according to the invention may be an electric motoror a generator for generating current, or also a combination of boththereof operating optionally either as motor or as generator. In thefollowing, reference will be made mainly to electric motors, but allstatements apply analogously to generators as well.

The electric machine according to the invention may be a rotary or alinear machine. In the following, reference will be made mainly torotary electric machines (“rotor part” instead of “moving part”), butall statements apply analogously to linear machines as well.

The electric machine according to the invention preferably iselectronically commutated, i.e. it has electronic components by means ofwhich current can be supplied to the winding coils for a respectivesuitable time phase (electric motor) or by means of which current can bewithdrawn from the winding coils at the respective suitable time phases.In the following, reference will be made mainly to electronicallycommutated machines, but many statements apply analogously also tomachines that are not electronically commutated.

In the electric machine according to the invention, there are thefollowing two basic possibilities of design: either the stator part isprovided with the winding coils and the moving part is provided with thepermanent magnets; this design provides the advantage that no currenthas to be be supplied to the moving part for the winding coils orwithdrawn from the winding coils, respectively. To the contrary, it isalso possible to provide the stator part with the permanent magnets andthe moving part with the winding coils.

In case of permanent-magnetically excited rotary electric motors,electrical current is supplied to the winding coils each time for“correct” time phases and each time with the “correct” sign. However, assoon as the rotor rotates, the permanent magnets (positioned e.g. on therotor) induce a voltage in the winding coils (positioned e.g. on thestator); this induced voltage normally is briefly referred to as EMF. Inprinciple, the EMF linearly increases with the speed of the rotor. Thisis due to the fact that the amplitude and the position-dependent path ofthe permanent-magnetic flux passing through the winding coils isconstant, whereas the speed of change thereof in terms of time changesso with the speed of rotation. A considerable improvement of the overallsystem consisting of machine and associated power electronics, however,would result if it were possible to take influence on the inducedvoltage at a given speed, in particular to reduce the increase towardshigh speeds and to realize in the ideal case a constant voltage over theentire speed range.

There have already been made attempts for taking influence on the amountof the voltage induced in the winding coils. There are known measuresusing mechanical means, e.g. splitting the stator into two relativelyrotatable stator parts, with the associated coils thereof beingconnected in series; splitting the rotor part into two relativelyrotatable rotor parts; axial displacement of the rotor in relation tothe stator. Moreover, there are known electrical measures, e.g. seriesconnection of two associated stator coils by means of electric phaseshifter; active displacement of the phase angle between current andinduced voltage by changing the time of commutation in the associatedpower electronics (exploitation of the inductive voltage drop); changingof the series/parallel connection of winding coils.

Most of the known measures are very complex and lead to partial resultsonly at the expense of disadvantages in other aspects.

For solving the technical problem mentioned, the permanent-magneticallyexcited electric machine according to the invention is characterized inthat there is provided a flux conduction liquid that is conductive formagnetic flux; and that in the region of the flux path assembly of thestator part and/or of the moving part, there is provided at least onefilling space which, for changing the magnetic flux conductivity of theflux path assembly, may have optionally more or less flux conductionliquid supplied thereto.

In the simplest case, the flux conduction liquid is a liquid that isloaded with magnetically conductive particles, e.g. iron powdermaterial, with chemical additives being provided to keep the conductiveparticles floating so that a permanently stable flux conduction liquidis provided. Flux conduction liquids are known per se and commerciallyavailable, e.g. from the company Ferrofluidics GmbH, Nürtingen, Germany.

When the quantity of flux conduction liquid in the filling space isreduced, the magnetic flux conductivity is reduced therein. As aconsequence, the amplitude of the magnetic flux through the windingcoils is reduced, thereby decreasing the voltage induced there. In mostof the practical applications, the quantity of so flux conduction liquidin the filling space will thus be reduced at high speeds of the machinesand increased at low speeds thereof.

Preferably, supplying of more or less flux conduction liquid to thefilling space comprises the utilization of a number, preferably a smallnumber, of discrete filling states of the filling space, preferably atleast the filling state “full” and the filling state “empty”. Inpractical application, the use of only the two filling states “full” and“empty” often is particularly preferred. With this embodiment, the meansfor changing the filling state can be formed in technically particularlysimple manner. It is true that there is no optimum matching in themiddle speed range, but at least in the especially important range ofhigh speeds there is achieved a full reduction of the induced EMFaccording to design.

As an alternative, it is preferred that the supplying of more or lessflux conduction liquid to the filling space comprises the utilization ofa continuous range of filling states of the filling space, preferablyinclusive of the final filling state “full” and the final filling state“empty”. This design permits fine matching of the magnetic fluxconductivity of the flux path assembly to the speed of the machine,however at the expense of higher expenditure for the technicalrealization. The term “continuously” is not supposed to mean that anyarbitrary filling state is actually utilized. It is merely supposed topoint out that a relatively large number of filling states that arerelatively close together is employed.

The flux path assembly provided with winding coils preferably isprovided with interruptions of the flux path assembly that serve asfilling spaces. In case of empty filling spaces, there is the maximumreduction of magnetic flux conductivity of the flux path assembly.

In the flux path assembly provided with winding coils, there arepreferably provided local recesses of the magnetic flux cross-sectionalarea that serve as filling spaces. This design often can be realized intechnically simpler manner than the design described in the precedingparagraph. With a suitable size of the recesses (i.e. depth or width,measured transversely to the longitudinal direction of the flux paththere, or width, measured in the longitudinal direction of the flux paththere), it is easily possible to obtain the desired reductions inmagnetic flux conductivity of the flux path assembly.

The flux path assembly provided with winding coils preferably isprovided with an under-dimensioned solid-material flux path assembly andat least one filling space for large-area up-dimensioning of the fluxpath assembly. As a concrete design in this respect, the possibility isto be indicated as an example that the magnetic flux cross-sectionalarea of iron can be increased considerably with respect to the overallmagnetic flux cross-sectional area by an adjacent filling space parallelthereto (when filled with flux conduction liquid), or not (when notfilled with flux conduction liquid). The term “large-area” is to pointout that the magnetic flux conduction liquid can not only be changedlocally at some isolated locations only (as in case of theafore-mentioned interruptions or recesses), but that this change coverseither the entire flux path assembly or at least a considerable partialsection of the flux path assembly.

Instead of the flux path assembly provided with winding coils, or inaddition to said assembly, the inventive variability of the magneticflux conduction liquid may be established at the flux path assemblyprovided with permanent magnets (preferably provided on the moving orrotor part).

The flux path assembly provided with permanent magnets preferably isprovided with interruptions of the flux path assembly that serve asfilling spaces. In case of circumferentially magnetized permanentmagnets and flux conduction elements between two adjacent permanentmagnets each, this preferably may have the result that distance spacesbetween permanent magnets and flux conduction elements are provided asfilling spaces.

In the flux path assembly provided with permanent magnets, there arepreferably provided local recesses of the magnetic flux cross-sectionalarea that serve as filling spaces.

The flux path assembly provided with permanent magnets preferably isprovided with an under-dimensioned solid-material flux path assembly andat least one filling space for large-area up-dimensioning of the fluxpath assembly.

The statements made hereinbefore with respect to preferred embodimentsof the flux path assembly provided with winding coils, apply analogouslyhere for the flux path assemblies provided with permanent magnets aswell.

In case of circumferentially magnetized permanent magnets and fluxconduction elements between two adjacent permanent magnets each, thereis furthermore a preferred design in which there is provided at leastone filling space for optionally creating a magnetic shunt on the sideof the permanent magnets and the flux conduction elements directed awayfrom the air gap. The magnetic shunt causes a different operating pointof the permanent magnets with a different distribution of the magneticfluxes, which has the effect of a lower air gap field strength. As aresult, there is again obtained a decrease of the voltage induced in thewinding coils, however in this case with an increase of the fluxconduction liquid in the filling space.

A technically particularly uncomplicated design often results if—as ispreferred—the filling space is connected to a circuit of the fluxconduction liquid. With this design, the air present in the fillingspace, upon increasing the flux conduction liquid in the filling space,may easily be expelled from this filling space. Upon reduction of thefilling state of the filling space, the possibility is present toprovide for a renewed flow of air into the filling space.

When the moving part has at least one filling space, it is preferredthat a pump for conveying the flux conduction liquid is arranged on orintegrated in the moving part. As an alternative, the pump for conveyingthe flux conduction liquid may be arranged separately from the movingpart and connected to the filling space via at least one passagewaypermitting relative movement. The possibility mentioned first as a ruleis mechanically simpler, but increases the weight and the volume of themoving part. The flux conduction system in general comprises a reservoirfrom which liquid is withdrawn in increasing the quantity of the liquidin the filling space and into which liquid is returned in reducing theliquid quantity in the filling space.

It is preferred to perform the increase or reduction of the quantity offlux conduction liquid in the filling space in automated manner, e.g. inthe manner of a control loop as a function of the rotational speed ofthe machine. In this regard, it will not be very expedient as a rule toreact on any small change in speed immediately with a change of theliquid quantity in the filling space. As a rule, it is sufficient toreact when the speed has changed by a considerable value and/or stablyfor a longer period of time.

In case of a machine with an external rotor, in which the fluxconduction liquid serves to provide a magnetic shunt, it is possible totake advantage of the automatic filling of the filling space with fluxconduction liquid due to centrifugal force, which is effected as aresult of a higher speed.

Preferably, the filling space and the flux conduction liquid are at thesame time constituent parts of a cooling system of the machine. Thecooling system of the machine can operate substantially with the fluxconduction liquid only, but combinations with another, liquid or gaseouscooling medium are possible as well. However, the invention provides forthe possibility of utilizing a liquid that is present anyway for thefunction according to the invention, namely the flux conduction liquid,at the same time for cooling purposes as well. In that event, there willpreferably be provided an extent of circulation of the flux conductionliquid that is in excess of the extent required for changing themagnetic flux conductivity of the flux path assembly. When the fluxconduction liquid at the same time fulfils a cooling function, it has tobe cooled down as a rule, e.g. by means of a heat exchanger and asecondary cooling liquid circuit or by means of a heat exchanger to air.

The machine according to the invention, when considering the case of arotary machine, may be designed either with, an internal rotor or withan external rotor. These two designs are machines with a cylindrical airgap. As an alternative, it is possible to have rotary machines with aplanar air gap in which stator part and rotor part are opposite eachother in axially spaced apart manner.

The electric machine according to the invention may be constructed inaccordance with the flux concentration principle in which a highermagnetic field strength is present in the air gap than at the exit areaof the permanent magnets. With respect to more detailed statementsconcerning the flux concentration principle, reference is made to EP 0331 180 A. There and further below in the present application, there arealso described more concrete embodiments of electric machines accordingto the flux concentration principle.

The invention and further developments of the invention will beexplained in more detail in the following by way of embodiments shownschematically in the drawings in which:

FIG. 1 shows a developed, cross-sectional view of a partial region of astator part of an electric machine;

FIG. 2 shows a developed, cross-sectional view of a partial region of astator of an electric machine according to another embodiment;

FIG. 3 shows a developed partial region of a cross-sectional area of anelectric machine according to another embodiment, illustrating a statorpart and a rotor part;

FIG. 4 shows a developed partial region of a cross-sectional area of anelectric machine according to another embodiment, illustrating both astator part and a rotor part;

FIG. 5 shows a developed partial region of a cross-sectional area of anelectric machine according to another embodiment, illustrating both astator part and a rotor part;

FIG. 6 shows a highly schematic longitudinal sectional view of part ofan electric machine.

The electric machines illustrated in FIGS. 1 to 5 are rotary electricmachines in which the stator part has the winding coils and the rotorpart has the permanent magnets. This is why the term rotor part, insteadof the more general term moving part, is used. Analogous linear machinesare conceivable immediately when FIGS. 1 to 5 are not considered as adeveloped view, but as longitudinal sectional view of a partial regionof the linear machine. As will be pointed out more clearly in thedescription further below, the embodiments according to FIGS. 1 to 5 areall machines with a cylindrical air gap. Considering a differentdirection of development, the drawing figures may also be understood asmachines with a planar air gap. The representations of FIGS. 1 to 5apply irrespectively of whether an electric motor or a current generatoris concerned. In the following description, the term machine will beused, however, it is to be pointed out here that the respectiveembodiment shown may be optionally either a motor or a generator.

The partial region of a stator part 2 illustrated in FIG. 1 has threestator poles 4 each provided with a winding coil 6. Illustrated by wayof a broken line is the location of an air gap 8 of the machine. Whenthe stator part 2 is conceived to have an annular curvature around anaxis 10 (which, as indicated by an arrow 10, is located in realityconsiderably further below with respect to the drawing sheet), the airgap 8 takes a cylindrical configuration; the development carried out forillustration purposes so to speak would be reversed thereby. However, ifthe axis 10 is conceived to be tilted by 90° in the drawing plane so asto extend from above downwardly, and then displaced from the drawingplane parallel in forward or rearward direction, a cylindrical curvatureabout this axis leads to a stator in which the free ends of the statorpoles 4 constitute a ring lying in a plane and the air gap 8 is a planarair gap.

It can be seen that the stator poles 4, at the side thereof remote fromthe air gap, do not merge with each other (which would create aconventional magnetic-flux return path there), but that an interruptionor break 12 is provided there between two adjacent stator poles 4 each.What has been referred to as flux path assembly (of the stator part) inthe preceding description, in the embodiment of FIG. 1, is the lining upof U-shaped iron paths, with an interruption 12 being present in eachhorizontal leg of the U-shape.

It can be seen that in each interruption 12, the end facing the air gap8 or the winding groove between two adjacent stator poles 4 isterminated by a sealing wall 14 in liquid-tight manner. The same holdsfor the end of the interruption 12 located to the rear of the drawingplane and to the end of the interruption 12 located in front of thedrawing plane.

All interruptions 12 are connected by a liquid channel 16 extendingalong the row of stator poles 4 on the side thereof directed away fromthe air gap. It is pointed out that the liquid channel 16, as measuredperpendicularly to the drawing plane, may have substantially the samewidth as the stator poles 4. In this case, the liquid channel itselfconstitutes a “filling space” or a “constituent part of the overallfilling space” in the sense of the invention. Alternatively, the liquidchannel 16, as measured perpendicularly to the drawing plane, may have arelatively small width; in this case, it has in essence just thefunction of optionally supplying liquid to the interruptions 12 orwithdrawing liquid from the interruptions 12. An additional and evenparticularly preferred alternative consists in providing a liquidchannel 16 each both on the face side of the stator poles 4 located infront of the drawing plane and on the other face side of the statorpoles 4 located to the rear of the drawing plane. With this design,liquid may be supplied to the interruptions 12 through one of thechannels 16, while liquid may be withdrawn from the interruptions 12through the other one of the two channels 16. The incorporation in aliquid circuit, the discharge of air from the interruptions 12, therenewed feeding of air to the interruptions 12 and other features arepossible in particularly simple manner.

The liquid illustrated by way of dots in the interruptions 12 and inchannel 16 is a magnetically conductive flux conduction liquid, In thefollowing, the term “flux conduction liquid” will be abbreviatedthroughout to “liquid” to render the description more concise.

If, as illustrated, the interruptions are filled completely with liquid18, a state is obtained that is not much different from the situation inwhich stator iron is contained in the liquid-filled regions (dependentin detail upon the conductivity of the liquid for magnetic flux). If, incontrast thereto, the liquid 18 is withdrawn completely from theinterruptions 12 and the channel 16, a state is obtained in which theflux path between each two adjacent stator poles 4 is interrupted, thuscreating a very considerable reduction of the EMF induced in the windingcoils 6 by the permanent magnets on the moving rotor part. There arepossible intermediate values by partly filled interruptions 12. Anyinterruption 12 constitutes a “filling space” (or in a differentconsideration, a part of an overall filling space) in the sense of theinvention.

The second embodiment according to FIG. 2 differs from the firstembodiment according to FIG. 1 merely in that, instead of interruptions12, there are provided recesses 20 on the side of the flux path assemblydirected away from the air gap. The individual stator poles 4 arephysically coherent via the stator iron bridging the recesses 20.Sealing as in case of the interruptions 12, by way of the wall 14, isnot required. When the recesses 20, for compensation purposes, are madewider (as measured from left to right in FIG. 2 and thus measured in thelongitudinal direction of the flux path) than the interruptions 12, acorresponding reduction of the magnetic flux conductivity of the fluxpath assembly can be achieved.

In the third embodiment according to FIG. 3, the variability of themagnetic flux conductivity is provided in the flux path assembly of arotor part 30. The stator part 2 is formed basically similar to thefirst and second embodiments, however, it has winding coils 6 on everyother stator pole 4 only and there is no pole head broadening and nofilling space or spaces for flux conduction liquid at the stator part 2.

The rotor part 30 is substantially cup-shaped (in so far illustratedbest by FIG. 6), with the developed-cylindrical partial regionillustrated in FIG. 3 consisting in essence of an iron sleeve 32, anouter wall 34 placed therearound while being spaced therefrom, acylindrical filling space 38 between iron sleeve 32 and wall 34, andpermanent magnets 36 mounted to the inside of the iron sleeve 32. Whenprogressing along the row of permanent magnets 36, the polarity thereofalternates. There is in alternating manner a north pole directed to theair gap 8 and a south pole directed to the air gap 8. Circumferentiallyadjacent permanent magnets 36 are connected magnetically by amagnetic-flux return path, which is provided by the iron sleeve. Theiron sleeve 32, provided with the permanent magnets 36, constitutes aflux path assembly of the rotor part 30, In the extreme case, the ironsleeve may be very thin in radial direction and may even be omittedcompletely.

When the filling space 38 between the iron sleeve 32 and the wall 34 isfilled with flux conduction liquid 18, the magnetic flux conductivity ofthe flux path assembly described is higher than in the event when thefilling space 38 contains no liquid 18, since together with the liquid18 the magnetic flux cross-sectional area of the flux path assembly iseffectively increased. The third embodiment makes good sense in case theiron sleeve 32 constitutes an undersized or under-dimensioned flux pathassembly that is up-dimensioned by the liquid 18 at low speeds.

It is pointed out that a construction as in case of the third embodimentcan also be realized on the stator part. Assume the recesses 20 shown inFIG. 2 to be closed by means of iron, but with the stator iron on theside directed away from the air gap being made so thin in its entiretyin radial direction that an under-dimensioning of the flux path assemblyis present.

On the other hand, the first embodiment and the second embodiment mayalso be realized at the rotor part 30. To this end, FIG. 3 should beconceived as having either interruptions in the iron sleeve 32 orrecesses radially outside on the iron sleeve 32, between two adjacentpermanent magnets 36 each.

The fourth embodiment according to FIG. 4 differs from the thirdembodiment on the one hand in that, instead of the iron sleeve 32 andthe radially magnetized permanent magnets 36, an alternatingsequence—when moving from left to right in FIG. 4 or in circumferentialdirection of the machine—of circumferentially magnetized permanentmagnets 36 and flux conduction elements 40 is provided.Circumferentially adjacent permanent magnets 36 are magnetized inopposite directions. The permanent magnets 36, in the cross-sectionalview of FIG. 4, are of trapezoidal shape having the short base sidedirected towards the air gap 8. Radially outside of the arrangement ofpermanent magnets 36 and flux conduction elements 40, there is providedan outer wall 42 supporting the permanent magnets 36 and the fluxconduction elements 40. Radially inside, there is provided a sealingwall 44.

Between each permanent magnet 36 and its two circumferentially adjacentflux conduction elements 40 there is provided a spacing gap 46. Radiallyoutside of the arrangement of permanent magnets 36 and flux conductionelements 40, a radially as thin as possible spacing gap 48 is presenttowards the outer wall 42, that serves merely for transporting theliquid 18. However, preferred is a construction without this spacing gap48, especially with a supply and discharge of the liquid 18 in axialdirection. The spacing gaps 46 together constitute a filling space forflux conduction liquid 18. When the filling space is emptied of liquid18, the spacing gaps 46 constitute local interruptions of the flux pathassembly of the rotor part 30. When the spacing gaps 46 are filled withliquid 18, a flux path assembly with high magnetic flux conductivity isformed.

The fifth embodiment according to FIG. 5 differs from the fourthembodiment in that there is no spacing gap 48 present between eachpermanent magnet 36 and its two adjacent flux conduction elements 40.Theoptional spacing gap 48 is expanded to a filling space 50 of largeradial thickness.

Due to this modification, the function of the machine is altered. Asthere are no spacing gaps 46, the flux path assembly of the rotor part30, also without liquid, is not under-dimensioned. When filling space 50is filled with liquid 18, magnetic shunts are established betweenadjacent flux conduction elements 40 via the liquid 18. The operatingpoint of the permanent magnets 36 is thus shifted, providing a differentsplitting of the fluxes, which has the effect of a lower air gap fieldstrength. As a result, there is established a reduction of the voltageinduced in the winding coils 6. The shunts described are illustrated byway of arrow lines 52. Arrow lines 54 indicate the “regular” magneticcircuits via the air gap 8 to the stator part 2 and back again.

FIG. 6 illustrates how a more complete flux conduction liquid system canbe conceived e.g. with a filling space configuration as in FIG. 3 or inFIG. 5. The filling space 38 or 50 is connected via a channel 62 to aliquid reservoir 64 (with partial gas volume in reservoir 64). If thereis more liquid 18 desired in the filling space 38 or 50, the liquid issupplied there from reservoir 64 via channel 62, and is fed in theopposite way when there is a lesser filling state desired in the fillingspace. Due to the centrifugal force, the liquid 18 is distributed in thefilling space as a radial outer layer. If desired, the filling space 38or 50 may be filled completely with liquid 18.

It is expedient in practical application to connect an additional liquidchannel to the in FIG. 6 right-hand axial face side of the filling space38 or 50, and to form a circulation system for the liquid 18, preferablyby means of a pump. Upon switching of the pump to a different suctionopening, it is then possible to pump in liquid or also air e.g. from theleft-hand face side in FIG. 6. By pumping liquid 18 in, the fillingstate of the filling space in increased, whereas by pumping air in, thefilling state is reduced. The discharge of liquid or air takes place onthe in FIG. 6 right-hand face side of the rotor part 30.

FIG. 6 also is an example to the effect that the flux conduction system,also inclusive of the pump, may be accommodated on the rotor part 30.When the flux conduction liquid system at the same time is to beconstituent part of the cooling system of the machine, cooling down ofthe liquid 18 is expediently provided for, e.g. by a liquid/air heatexchanger 66 on the outside of the rotor part 30.

When the reservoir 64 and the pump, not illustrated, are to be arrangedseparately from the rotor part 30 and in stationary manner, the channel62 has to be connected outwardly to the pump and the reservoir 64 e.g.by means of a rotation passage through the axis 60 of rotation.

Furthermore, it is easily conceivable by way of FIG. 6 how a completeflux conduction liquid system for the stator part 2 can be designed. Inthis event, reservoir 64, pump, channel 62 and optionally heat exchanger66 are simply provided on the stator part 2 in stationary fashion.

Although in all embodiments the filling spaces were provided either onthe stator part 2 or on the rotor part 30, it is emphasized that it ispossible to provide the filling spaces both on the stator part 2 and onthe rotor part 30.

As a rule, the most important operating states will be “filling space orspaces full” and “filling space or spaces empty”. However, it is alsopossible to employ discrete intermediate filling states or a quasicontinuous variation of the filling states. Partly full filling statesare conceivable best in rotary machines in practical application whenthe stator part 2 or the rotor part 30 is circumferentially divided intoa plurality of sectors and each sector is provided with a supply channelof its own and, optionally, with a discharge channel of its own.Especially in case of the fourth embodiment, a partial filling statethat is circumferentially balanced automatically presents itself due tothe rotational movement of the rotor part 30.

In case the machine is a generator, the purpose according to theinvention is not a reduction of the induced EMF at high speeds, but thepossibility of reducing the speed dependency of the value of the voltagegenerated.

1. A permanent-magnetically excited electric machine comprising a statorpart (2) and a moving part (30) movable relative to the stator part (2),as well as an air gap (8) between the stator part (2) and the movingpart (30), with one of said stator part (2) and said moving part (30)having a flux path assembly for magnetic flux and winding coils (6) andthe other one of said stator part (2) and said moving part (30) having aflux path assembly for magnetic flux and permanent magnets (36), and inwhich in the region of the flux path assembly of the stator part (2)and/or of the moving part (30), there is provided at least one fillingspace (12; 16; 20; 38; 46; 48; 50) for receiving flux conduction liquid(18) that is conductive for magnetic flux, characterized in that, forchanging the magnetic flux conductivity of the flux path assembly, thequantity of the flux conduction liquid (18) in the filling space (12;16; 20; 38; 46; 48; 50) may be changed during operation of the machinein dependency on the rotational speed of the machine.
 2. A machineaccording to claim 1, characterized in that supplying of more or lessflux conduction liquid (18) to the filling space comprises theutilization of a number of discrete filling states of the filling space,preferably at least the filling state “full” and the filling state“empty”.
 3. A machine according to claim 1, characterized in thatsupplying of more or less flux conduction liquid (18) to the fillingspace comprises the utilization of a continuous range of filling statesof the filling space, preferably inclusive of the final filling state“full” and the final filling state “empty”.
 4. A machine according toclaim 1, characterized in that the flux path assembly provided withwinding coils (6) is provided with interruptions (12) of the flux pathassembly that serve as filling spaces.
 5. A machine according to claim1, characterized in that the flux path assembly provided with windingcoils (6) is provided with local recesses (20) of the magnetic fluxcross-sectional area that serve as filling spaces.
 6. A machineaccording to claim 1, characterized in that the flux path assemblyprovided with winding coils (6) is provided with an under-dimensionedsolid-material flux path assembly and at least one filling space forlarge-area up-dimensioning of the flux path assembly.
 7. A machineaccording to claim 1, characterized in that the flux path assemblyprovided with permanent magnets (36) is provided with interruptions ofthe flux path assembly that serve as filling spaces.
 8. A machineaccording to claim 7, characterized in that circumferentially magnetizedpermanent magnets (36) and flux conduction elements (40) are providedbetween two adjacent permanent magnets (36) each; and that distancespaces (46) between permanent magnets (36) and flux conduction elements(40) are provided as filling spaces.
 9. A machine according to claim 1,characterized in that the flux path assembly provided with permanentmagnets (36) is provided with local recesses of the magnetic fluxcross-sectional area that serve as filling spaces.
 10. A machineaccording to claim 1, characterized in that the flux path assemblyprovided with permanent magnets (36) is provided with an under-dimensionsolid-material flux path assembly (32) and at least one filling space(38) for large-area up-dimensioning of the flux path assembly.
 11. Amachine according to claim 1, characterized in that circumferentiallymagnetized permanent magnets (36) and flux conduction elements (40) areprovided between two adjacent permanent magnets (36) each; and that onthe side of the permanent magnets (36) and the flux conduction elements(40) directed away from the air gap, there is provided at least onefilling space for optionally providing a magnetic shunt.
 12. A machineaccording to claim 1, characterized in that the filling space isconnected to a circuit of the flux conduction liquid (18).
 13. A machineaccording to claim 1, characterized in that the moving part (30) has atleast one filling space; and that a pump for conveying the fluxconduction liquid (18) is arranged on the moving part (30).
 14. Amachine according to claim 1, characterized in that the moving part (30)has at least one filling space; and that a pump for conveying the fluxconduction liquid (18) is arranged separately from the moving part andis connected to the filling space via at least one passageway permittingrelative movement.
 15. A machine according to claim 1, characterized inthat the filling space and the flux conduction liquid (18) at the sametime are constituent part of a cooling system of the machine.